# What is Sound pressure: Definition and 27 Discussions

Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone. The SI unit of sound pressure is the pascal (Pa).

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1. ### Sound absorption/Acoustuic attenuation coefficeint (α(ω)) of PVC foam?

I am currently doing a physics experiment to find the frequency-dependent attenuation coefficient (α(ω) )of pvc foam, are there any verified/reliable sources that show the attenuation coefficient α(ω) of pvc foam or materials in general? Best I found is this...
2. ### I Sound pressure and inverse distance law

Hello, I am confused as to how to think about sound pressure and the distance from a sound source. Let's assume that a sound wave is omnidirectional and propagating away from a source in a sphere. We have the following two equations: Pressure = Force/Area Intensity = Power/Area Many texts...

5. ### Calculate Sound Pressure Level

Homework Statement Spaker located at 90 feet from a auditorium chair. The sound pressure level at the chair is 70 dB. The first reflection from the roof takes 200ms to get to the chair. What distance does the first reflection travel to get to the chair if the room temperature is 303.15 K? What...
6. ### Why Does Doubling Speakers Double Sound Pressure with Less Power?

Hello, I have a question that I've been struggling to find an answer to / understand. Probably because my understanding of physics is quite limited :) Before I ask the question, these are the things I take as facts, so please correct me if something is wrong: 1. A speaker in half space...
7. ### Tympani in a concert hall: calculating Sound Pressure Level (SPL) and delay

Homework Statement Hello. I have a problem, which is as follows: A seat in a concert hall is 84 ft from the tympani. The tympanist strikesa single note. The sound pressure level of the direct sound of the note at the seat is measured to be 55 dB. The first reflection from the nearest sidewall...
8. ### Estimating sound pressure (in an MRI scanner)

Hello, excuse me if these happen to be basic questions, but I'm a psychologist/neuroscientist in training without any particular experience in physics, and I am just confronted with a very specific problem. I need to measure the sound pressure experienced inside of an MRI scanner...
9. ### Sound Pressure in Partial Vacuum

Is there a good description or formula regarding how the sound pressure from a constant source depends upon ambient pressure? That is, if I were to conduct an experiment where I put a source and a microphone in a container, and then change the pressure in that container with a pump, assuming...
10. ### Units of sound pressure level, example: 120 dB re 20 μPa

I am trying to do a calculation using a value of -211dB re uPa/V , are these SI units? i.e. if OCV = -211db re uPa/V and I have RL = 20log(Vrms) - OCV Do I need to convert the OCV to standard units before putting it in the equation? Wiki isn't so clear about this:
11. ### How to find the sound power in a collision?

How would you go about calculating the sound power and sound pressure given the pressure (as in collisions [force/area]) of the collision, kinetic energy in the collision, velocities of both objects, densities and masses. Is this possible? Is the pressure of the collision equal to the sound...
12. ### Calculating Sound Pressure Level As Distance Changes

Homework Statement The sound pressure level is 80db at a distance of 30 meters. What is the dBSPL at 60 meters? Homework Equations My book has provided me the following formula: dBSPL = dBr-20log(di/dr) - but it has not explained what "di" and "dr" are.The Attempt at a Solution I've been...
13. ### Sound pressure level at vacuum cleaner and earphones

Hello, I have read that vacuum cleaner makes 70 dBa and earplugs can easily go beyond this. The problem I have is that I can hear my neighbor's vacuum cleaner thru wall easily. But if I set my mp3 player at max (should be around 100dBa according to manufacturer) I can heard this at few...
14. ### Why does sound pressure vary with 1/r?

I didn't follow the template because this is more of a conceptual question that I can't get a clear answer for. I understand that sound intensity varies with 1/r^2 because the total intensity at a point in the wave is constant and if you have spherical propagation then the area of the surface...
15. ### Sound Pressure inside the cabin

Hello, I am trying to measure the sound pressure inside a cabin. I placed 2 microphones to measure it using octave band. For each frequency i have two sound pressures ..is it possible to take the average of them ? for example add the 2 sound pressure for the 2 microphones and divide...
16. ### Is there a formula for calculating SPL?

Hi. Is there a formula for calculating SPL? The information I have is Frequency of pitch, dB level of pitch and 0dB as 20uPa. TIA
17. ### Overall Sound Pressure Level between two Frequencies

Homework Statement The band levels for a noise are 70 dB reference 20\muPa at 31.5 Hz and decrease 3 dB for each octave. Find the overall sound pressure level between 31.5 and 8000 Hz and the A-weighted sound pressure level for this frequency range. Homework Equations...
18. ### Sound waves and sound pressure

Homework Statement Consider a sound wave in air of density 1.2 kg/m3. The displacement wave has the form s(x,t)=smaxcos(kx-\omegat) where k=8.79rad/m, \omega=3021.6 rad/s and smax=2.51 x 10-7m. Calculate the sound pressure \DeltaP(x,t) of this wave at x=0.282m and t=0.00137s. Answer in units...
19. ### Calculate sound pressure inside a cavity

How do I calculate sound pressure inside a channel. I have a channel of 40 mmx 40 mm cross sectional area. I have placed a sound source on one of the side wall that resonates at 50 Khz. I know the voltage required to drive the transducer. The transmit voltage response of the transducer is 110...
20. ### Why does particle displacement A increase sound pressure?

pressure=p(x,t)=BkAsin(kx-ωt) http://www.physics.unomaha.edu/Sowell/phys2120/Lectures/Sound/Sound.pdf Surely, when loudness-intensity-pressure increases, so does the maximum displacement A of the speaker. Wrong thread title. My question is: Why increasing the maximum molecule...
21. ### Lowering Sound Pressure: Techniques and Considerations

How to lower sound pressure (i.e. the volume of a sound)?
22. ### Determing Sound Pressure Levels (SPL)

1a. Determine the Sound Pressure level at a point due to a machine running alone if the measurements at the point with the machine 'on' and 'off' are 94 dB and 90 dB re 20 uPa respectivele b) Consider white noise where P(f) = A for f >= 0. Show that the SPL's corresponding to successive 1/N...
23. ### What Is the Optimal Position for an Acoustic Barrier to Reduce Road Noise?

Hi, I am new to this forum and I'm not sure if I have selected the correct area to post this question. If you think I should move it then let me know! As you can see, I have worked out part of the question but I am stuck when it comes to doing the second half. Any help would be appreciated...
24. ### Validity of a Formula for Superposition of Coherent Sound Waves

Hi, I am trying to determine the validity of a formula I came across... I have not seen it anywhere else and I can't be sure wether it's valid or not... Consider a number of sound pointsources positioned on a line. The soundwaves coming from each sound source are all in phase (at time t =...
25. ### Sound pressure level and sound intensity level

Hi all. A very simple question: what is the difference between sound pressure level and sound intensity level? It seems to me that sound presssure level also measure the "energy" since it is p^2, which shall be related to energy... If it is so, it seems that sound pressure level shall be the...
26. ### Sound Pressure Calculations for a Baby and Parents

Homework Statement A baby's mouth is a distance of 35.0 cm from her father's ear and a distance of 1.52 m from her mother's ear. Child Sounds <------------0.35m-------->Father X <----------------------------1.52m-----------------> Mother Homework Equations I(Father) =...
27. ### Sound pressure level magnitude question.

Hey all, I've got an audio related question for you guys/gals: I understand the logarithmic relationship to SPL, but would someone help me out with a simple question and post a formula as to how you arrive at an answer? Assuming a start value of 150 decibels, what pressure level would...